Ioneer Ltd has achieved what it says is a further material improvement in project economics for its 100%-owned Rhyolite Ridge lithium-boron project in Nevada, USA, mainly through reducing the leach retention time within its planned process flowsheet.
By reducing leach retention time from three days to two days, and now to one and a half days, while using the same quantity of acid, the company estimates it will achieve material increases in lithium and boron production.
Throughout 2025, Ioneer has focused on increasing lithium yield (the quantity of lithium carbonate produced per tonne of sulphuric acid consumed) and optimising reagent efficiency.
The increased lithium production means the project will produce approximately 9,500 t/y of lithium carbonate/hydroxide that is not committed under existing off-take agreements, Ioneer says.
The project has a stable overall operating cost structure to produce lithium carbonate and battery-grade lithium hydroxide due to the scale and reliability of its boric acid revenue. Boron has remained one of the most stable natural resource commodities over many decades, according to the company, with its pricing assumptions remaining unchanged with a minimal increase in initial capital expenditure (A$15 million ($9.9 million)).
The updated stage one operation with reduced leach times and higher plant throughput resulted in materially improved project economics. The updated findings position Ioneer, on a lithium carbonate equivalent (LCE) basis, in the lowest cost quartile for lithium production globally with an estimated all-in sustaining cash cost to produce battery grade lithium hydroxide of $4,628/t net of expected boric acid revenue in the first 25 years, the company says.
“By cutting our leach processing time in half, Ioneer will now deliver more critical minerals faster to our partners as we collectively work to strengthen American critical mineral supply chains,” Bernard Rowe, Managing Director, Ioneer, said. “The Rhyolite Ridge lithium-boron project continues to exceed our high expectations with its unique mineralogy and project economics. The need for additional production and processing has never been greater, and Rhyolite Ridge continues to deliver.”
Ioneer developed its newest mine plan based on the higher processing rate leading to an updated ore reserve and mineral resource also being reported today. The overall reserve and resource numbers are largely unchanged from the previous August 2025 estimate, which yielded higher boron and lithium output.
In June 2025, Ioneer published an Association for the Advancement of Cost Engineering Class 2 capital cost estimate (-10%, +15%) with approximately 70% of the project’s engineering complete of $1.668 billion, including a 10% contingency. The changes announced today do not materially impact the capital cost estimate or the processing plant design, increasing the capital cost estimate by just $15 million.
At a production rate of 3.4 Mt/y, the company estimates it will achieve lithium carbonate equivalent (LCE) production of around 20,400 t/y, plus some 70,700 t/y of boric acid. From year three onwards, it is also guiding for around 23,200 t/y of lithium hydroxide output.
Rhyolite Ridge is also expected to be the first greenfield mining site in the United States to use automated haul trucks from the outset, leveraging Cat’s MineStar Command for hauling AHS on a fleet of Cat 785 haul trucks.
Ioneer says: “Following the success of numerous international implementations, automation is expected to improve safety and reduce operating and capital costs.”
The next steps for the project, as outlined by Ioneer, are secure equity financing to sit alongside US Government debt (A$996 million); complete a final investment decision (FID) once equity and debt are in place; start the construction phase, which is expected to take approximately 36 months (including procurement of long lead items), achieve first production, some 36 months on from FID; and assess pathways to future growth.
